What would be the result of an AI that does not find any pattern according its available methods of pattern recognition?
During my master thesis I struggled with this issue.

In strict sense, a real AI would be able to say, my sensors (or some of them) are gathering data i cannot understand (yet), and would ideally have a routine what to do whith such cases and ideally one day, even understand that data. But it would most probably now, if that is happening outside in the real world, or if it's due to damaged or wrong sensors.
But that broadly depends how it was programmed, so your use case would have to be further defined: what specific AI are we talking about, what can it do, what not, how is it built.

AI is actually able to reproduce
a) a subset of an adult's intelligence (speach, face recognition, etc.) but just on a case by case basis
b) or, if you seak to build a full grown intelligence, it has to go thorugh the development stages as humans (eyesight, voice, imitation, learning, etc.)
So AI is still in babysteps and is not even able to reproduce let's say an adolescent behaviour, or to reproduce the human evolution of a baby to an adolescent.

So, after a long speach, to come back to your original question: At the very moment an AI is not able to decide by itself, if it has no method to analize the data, if the data analized are too random, or if one of it's sensors is giving random input.
Perhaps in some years there are better methods, but at the moment, machines, as babys or childs, need adults hands to teach and show them what to do in what case and how to difference each use-case. Which often means that they would need to add new modules to the AI, which, nowadays is still far away from building anything we could really define as "intelligent" or even "artificially intelligent" (PD: Intelligence here means by ways much more than plain rationality)

I deeply recommend some books of Andy Clark concerning filosofical issues and AI:
e.g. "Being there: Putting Brain, Body and World together". Andy Clark is a filosofer which takes a deeper look at AI, the human brain, cognition sciences, filosofy, psychology, sociology, etc.